The present invention relates to a heat exchange assembly, and more particularly to a plate heat exchange assembly which may be optionally utilized as a liquid-to-gas heat exchanger, a low-flow internally-cooled liquid-desiccant absorber, a liquid-desiccant regenerator or an evaporatively-cooled fluid cooler.
Heating, ventilating, and air conditioning (HVAC) systems regulate ambient conditions within buildings for comfort. Such systems provide control of the indoor environment in a given space to create and maintain desirable temperature, humidity, and air circulation, for the occupants. One important component found in such systems is a heat exchanger which is a device used for transferring heat from one medium to another without allowing the media to mix.
One type of heat exchanger comprises a plurality of plates arranged in a spaced apart relationship by spacers. The space between adjacent plates provides a flow path for a heat transfer fluid. Each of the plates comprises a double walled board of metal or plastic, the walls being spaced-apart by partitions that form a plurality of internal passages therein. The partitions defining the internal passages provide a fluid flow path for a second heat transfer fluid. Examples of the use of such heat exchangers and details of their construction and operation are disclosed in U.S. Pat. No. 5,638,900 and U.S. Pat. No. 6,079,481, each of which is incorporated herein by reference.
U.S. Pat. No. 5,469,915 discloses a heat exchanger comprising a plurality of plates (also referred as xe2x80x9cpanels) arranged in a spaced apart manner. Each plate comprises a plurality of open-ended tubular members oriented in a planar arrangement sandwiched between a pair of thin, plastic films laminated thereon. A manifold is mounted to each open end of the plates. A heat transfer fluid is supplied to the plates from one manifold and exits the plates through the other manifold. In one embodiment, each manifold has multiple orifices into which the ends of the plate""s tubes are inserted and sealed. In another embodiment, each manifold is composed of two pieces, each piece with semicircular recesses that match the contour of the tubes. The ends of the plate""s tubes are clamped between the two halves of the manifold so that the ends of the plate""s tubes are completely contained within the manifold and the manifold and plate form a leak-tight assembly. For either embodiment of the manifold, a heat exchanger assembly composed of two or more plates can be made by stacking and joining together the manifolds.
U.S. Pat. No. 4,898,153 discloses a solar heat exchanger constructed from a double-walled plate with multiple internal flow passages. It is further disclosed that the ends of the plate are coupled to end components which provide recesses for turning a fluid flowing through the plates 180xc2x0 and outlet and inlet fittings are attached to the end components.
In an HVAC system, a dehumidifier may be used to extract moisture from the process air to yield relatively dry air. The air to be processed is usually dehumidified by cooling and/or by dehydration. In a dehydration process, air is usually passed through a device referred to as an absorber which typically includes chambers containing an absorptive material such as, for example, silica gel or calcium chloride. One type of absorber referred to herein as a liquid-desiccant absorber, utilizes a liquid desiccant, or drying agent, to remove water vapor from the air being processed. An example of a liquid-desiccant absorber and further details of its operation are disclosed in U.S. Pat. No. 5,351,497, incorporated herein by reference.
Liquid-desiccant absorbers typically include a porous bed of a contact medium saturated with a liquid desiccant. As the desiccant flows and permeates throughout the bed, it comes into contact with the water-containing air flowing therethrough. The desiccant, which by definition, has a strong affinity for water vapor, absorbs or extracts the moisture from the process air.
During the dehumidification process, heat is generally released as the water vapor condenses and mixes with the desiccant. The total amount of heat generated usually equals the latent heat of condensation for water plus the heat generated by mixing the desiccant and water. In a typical absorber, the heat of mixing will be about an order of magnitude smaller than the latent heat of condensation. The heat released during dehumidification raises the temperature of the air and desiccant. The air exits the absorber with approximately the same enthalpy as when it entered. For example, air enters the absorber at 80xc2x0 F., 50% relative humidity (31.3 BTU/lb enthalpy) and leaves at 97xc2x0 F., 20% relative humidity (31.5 BTU/lb enthalpy). In this configuration, the absorber functions strictly as a dehumidifier.
The absorber may be incorporated into an air-cooling system. By cooling the desiccant and the process air through a heat exchanger utilizing a coolant or refrigerant, the process air exits the absorber at a lower enthalpy and relative humidity than when it entered, thus generating a desirable net cooling effect. Absorbers utilizing such coolant assemblies often exhibit increased dehumidification capacity and efficiency over those that do not. However, prior art internally-cooled absorbers are typically more difficult and expensive to fabricate. In addition, such absorbers often experience difficulties in keeping the respective heat exchanging fluid streams and liquid desiccant separate and apart due to persistent leakage problems.
It would therefore be a significant advance in the art of heat exchangers to provide a heat exchange assembly which can effectively maintain the respective heat transfer fluids or media separate from one another and which can be constructed effectively from corrosion-resistant materials in a configuration that may be utilized in a wide variety of heat transfer systems, including, but not limited to, liquid-to-gas heat exchangers, internally-cooled liquid-desiccant absorbers, and evaporatively-cooled fluid coolers.
The present invention is generally directed to a heat exchange assembly which comprises:
a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane;
a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180xc2x0 turning of the fluid within the plate to create a fluid flow path between points of entry and exit of the fluid; and
at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.
In another aspect of the present invention, there is also provided a heat exchange assembly which comprises:
a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane;
a plurality of end-piece members equaling the number of the plates, each of the end-piece members includes a recessed region adapted to fluidly connect and couple with the first end of the plate, and further adapted to be affixed to respective adjacent end-piece members in a stacked formation, and further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180xc2x0 turning of the fluid within the plate to create a fluid flow path between points of entry and exit of the fluid;
fluid turning means at the first end of the plates for turning the flow of fluid into the plates; and
a fluid supply inlet and a fluid discharge outlet each associated with the affixed end-piece members so that the heat transfer fluid travels in parallel paths through each respective plate.